Despite how remarkable our brains are, they simply can’t process all of the information they’re faced with. You have to be able to process relevant information quickly whilst suppressing or filtering out less relevant, distracting information. Dr Duje Tadin
Intelligence involves more than a brain able to process information quickly, it requires the ability to automatically select only the most relevant information for processing, according to Dr Duje Tadin...
University of Rochester and Vanderbilt University scientists have identified a simple visual task that can predict IQ test scores. The paper, published this week in the Cell Press journal Current Biology, describes the relationship between intelligence and the brain’s ability to disregard irrelevant or distracting visual information.
The task, which quantifies the unconscious ability of the brain to filter out background motion, is the first solely sensory test to exhibit a strong correlation with IQ.
Senior author Dr Duje Tadin, an assistant professor in the Department of Brain & Cognitive Sciences at Rochester, led the study alongside first author Michael Melnick, a doctoral candidate in the University’s Center for Visual Science.
"This was one of those cases where you discover something that you weren’t planning on," said Dr Tadin in an interview with Department of Brain & Cognitive Sciences at Rochester, led the study alongside first author Michael Melnick, a doctoral candidate in the University’s Center for Visual Science.
" you="">ScienceOmega.com. "It wasn’t an accident, but it was based on a hunch that turned out to be true.
"People have been trying to find a link between basic perceptual processing and IQ going all the way back to Sir Francis Galton, and the effects people have found have always been much weaker than those we observed in our first study."
High IQ individuals automatically biased
The researchers report on two experiments in the paper, the first of which emerged from an unrelated study but which gave Dr Tadin and his colleagues an inkling that there might be a link between IQ and an effect called ‘spatial suppression’. The experiment, which had a small sample size of only 12 people, returned a correlation strong enough to make the investigators suspicious: it looked to strong to be true at 0.64.
"The next step was to run a completely new study from scratch with a larger sample size to test this more carefully," Dr Tadin said. "Study two involved a sample of 53 people, and to our surprise, the effect was even stronger."
As well as taking a standardised intelligence test, the subjects watched brief video clips of moving black and white bars on a computer screen. The size of the stimulus they were presented with varied, as you can see in the video. All the participants had to do was say which direction the bars were moving in. If they answered correctly, the video duration was shortened.
"High IQ people do really well when the image is small, but they struggle even more than lower IQ individuals when the object is large and more background-like," explained Dr Tadin. "What this tells is with regards to motion perception is that the visual system of high IQ individuals is automatically biased to process smaller moving objects and to ignore background movement."
Importantly, this is not a wilful suppression of background motion. The participants were not told to ignore the background – they were instructed to do their best regardless of the size of the stimulus. So what are the implications of these findings for the way we think about intelligence and IQ?
"Ever since Galton, people have found that an efficient brain is one that processes information quickly," said Dr Tadin. "That makes sense; if you think about computers, the faster the chip you have the better your computer will perform. Previous studies have focused on processing speed, and people with a higher IQ tend to do better on speeded perceptual tasks. The conclusion of those studies was that people with higher IQs are faster at processing information.
"We are not arguing with that, but it’s not the whole story. Despite how remarkable our brains are, they simply can’t process all of the information they’re faced with. You have to be able to process relevant information quickly whilst suppressing or filtering out less relevant, distracting information."
Spatial suppression not directly responsible for IQ
Dr Tadin and his colleagues hope to improve on the task used in their experiments, utilising its very simple, visual format to come up with a non-verbal predictor of IQ scores and hence a non-verbal way to measure intelligence.
"This could be used in the context of studying intelligence in people with mental disabilities or those who don’t have a good command of language," he told me. "It could also be useful if you are worried about cultural biases of certain IQ tests."
The team would also like to look at the neurochemistry of different individuals in the part of the brain involved in the task. When the brain suppresses information, there is necessarily an inhibitory process going on in the brain to prevent neurons responding to that information. It is possible to use MRI-type techniques to measure the concentration of the relevant neurotransmitters in order to judge whether individual differences correlate to IQ scores.
"I want to be very careful not to argue that the phenomenon of spatial suppression in motion perception is directly responsible for intelligence," concluded Dr Tadin. "But given the brain is composed of many different networks, it may be that this is part of the network that also includes brain areas associated with intelligent cognition."
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